I don’t know why it comes as a surprise every year; but as soon as the pumpkins are sold out and the fireworks over, supermarkets start playing Noddy Holder and for the next month and a half we are reminded constantly of the upcoming festive season. The desperate panic felt as I realise how many presents I need to buy is dampened only by copious amounts of mulled wine. There is, however, one person for whom I actually look forward to buying a Christmas present; my godson Sam. Sam is four years old and extremely passionate about trains, fire engines, tractors…in fact, give him any sort of miniaturised mode of transport and he’ll be happy for hours. This love of miniature machines is typical for a boy of his age whilst many of his female contemporaries will be putting altogether different toys on their Christmas list: dolls, tea sets, play kitchens to name but a few. Indeed, once again this year the majority of young boys and girls will have their stockings filled with gender-appropriate toys, but what causes these preferences?
Last year, Dr. Laura Nelson (a neuroscientist) persuaded London’s largest toy shop ‘Hamleys’ to stop marketing their toys as being either ‘for girls’ or ‘for boys’. She felt that such marketing influenced the types of toys children chose, therefore reinforcing gender stereotypes: girls playing with tea sets encourages domestic, passive playtime, whereas boys might engage in more active and aggressive play if given a pirate ship. While we already assume that environmental factors (toys, parents, friends) can influence a child’s gender-identity, are there any biological reasons why girls like ‘sugar and spice and everything nice’, while boys are happier playing with a lorry that turns into a robot?
Since it would be very hard, not to mention unethical, to hide a child away from all gender-biasing environmental influences, the majority of current research is based on animal studies; specifically monkeys! Since most monkeys have no interest to advertising campaigns and few have played with a teddy or toy car before, they make pretty good ‘naive’ experimental subjects. Prof. Melissa Hines and her fellow scientists from Cambridge allowed male and female vervet monkeys to ‘take their pick’ of masculine and feminine children’s toys, then recorded how long they spent playing with each one. As it turns out, female vervet monkeys spent more time with the typical girls’ toys, while male monkeys spent more time with typical boys’ toys. This sex-determined preference for different types of toy suggests that there could actually be fundamental differences between male and female brains; perhaps not just in monkeys, but in humans too.
So does gender change the wiring of a child’s brain, biasing their choice towards more gender-appropriate toys? Professor Gerianne Alexander studied three month-old babies – or rather, how these babies looked at toys. The longer a baby looks at something, the more he or she is believed to like that object. The length of babies’ glances at either dolls (feminine), trucks (masculine) or balls (neutral) were measured and then compared to the level of testosterone they were exposed to in the womb. Testosterone is made by both boys and girls but boys produce much more since they have… well, testes. Interestingly, Gerianne found that the level of testosterone in the womb correlated with how much the babies liked typically masculine toys. So the lads swimming around in more testosterone looked longer at the trucks, while girls who weren’t exposed to high levels of testosterone looked longer at the dolls.
Incredibly enough, in a similar experiment with newborn babies (conducted just 24 hours after birth) Prof. Simon Baron-Cohen and his colleagues found that, even at this early time-point, (at least the earliest possible considering hospital guidelines), there seems to be biological differences between the sexes. These studies suggest that the level of circulating testosterone in the womb may be enough to impact brain development and possibly behaviour, even before Christmas TV adverts can brainwash them.
Further proof of the gender-biasing effect of prenatal testosterone comes from cases of congenital adrenal hyperplasia (CAH). CAH is a genetic disorder which leads to the overproduction of testosterone. CAH is usually diagnosed at birth and can be successfully treated with steroids. Children suffering from this disorder usually go on to lead a totally normal life, despite their brain’s prenatal exposure to high levels of testosterone. Interestingly, though, Prof. Hines has found that girls with CAH tend to be tomboys through their childhood. They are seen to play more like boys, favouring ‘rough and tumble’ games and typical boys’ toys over more feminine play times. So, levels of prenatal testosterone seem to predict toy choice more accurately than the actual sex of the child.
I should emphasise that while prenatal testosterone levels might correlate well with the tricky choice of Action Man vs. Barbie, it doesn’t necessarily mean that testosterone causes kids to pick one or the other. Impatient parents can’t just inject their kids with testosterone to make Christmas shopping easier. It’s also likely that the timing of exposures to certain hormones may influence the brain in different ways. What’s interesting, though is that something as ubiquitous as toys can be used as a way of investigating the science behind gender-stereotyped behaviours. Also, something tells me my godson would have plenty of excuses to be ungrateful if I get him a My Little Pony this year. Best start looking for a space rocket…
Post by: Natasha Bray